title: Involvement of auxin distribution in root nodule development of Lotus japonicus.
abstract: The symbiosis between legume plants and rhizobia causes the development of new organs, nodules which function as an apparatus for nitrogen fixation. In this study, the roles of auxin in nodule development in Lotus japonicus have been demonstrated using molecular genetic tools and auxin inhibitors. The expression of an auxin-reporter GH3 fused to β-glucuronidase (GUS) was analyzed in L. japonicus roots, and showed a strong signal in the central cylinder of the root, whereas upon rhizobium infection, generation of GUS signal was observed at the dividing outer cortical cells during the first nodule cell divisions. When nodules were developed to maturity, strong GUS staining was detected in vascular tissues of nodules, suggesting distinct auxin involvement in the determinate nodule development. Numbers and the development of nodules were affected by auxin transport inhibitors (1-naphthylphthalamic acid, NPA and triindobenzoic acid, TIBA), and by a newly synthesized auxin antagonist, α-(phenyl ethyl-2-one)-indole-3-acetic acid (PEO-IAA). The common phenotypical alteration by these auxin inhibitors was the inhibition in forming lenticel which is normally developed on the nodule surface from the root outer cortex. The inhibition of lenticel formation was correlated with the inhibition of nodule vascular bundle development. These results indicate that auxin is required for the normal development of determinate nodules in a multidirectional manner.
authors.affiliation: Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji 611-0011, Japan.
authors.forename: Kojiro
authors.initials: K
authors.lastname: Takanashi
authors.forename: Akifumi
authors.initials: A
authors.lastname: Sugiyama
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
mesh_terms: D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D000070116:Lotus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism* / Q000382:microbiology; D009586:Nitrogen Fixation / Q000187:drug effects; D010797:Phthalimides / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000378:metabolism; D012231:Rhizobium / Q000254:growth & development; D053204:Root Nodules, Plant / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D007210:Indoleacetic Acids; D010797:Phthalimides; D010937:Plant Growth Regulators; C002687:alpha-naphthylphthalamic acid; C030737:indoleacetic acid; D005966:Glucuronidase